Apples – a lesson in variation and artificial selection

One of our science themes this month has been ‘plants’, and this week we supported this theme with a couple of Mystery Science lessons about why some plants grow fruit, and why some apples are red and others green. The apples lesson was a really great way of introducing the idea of how we get from a tiny, sour wild crab apple to a big juicy sweet eating apple via variation and artificial selection.

Apple tasting experiment

I’m sharing the practical experiment we did for this lesson as it was a lot of fun, and perfect to do with kids of any age (or adults for that matter – just add in some cheeses and wine and you’ve got a party). We went to a supermarket that I knew stocked lots of different varieties of apples and the boys chose two apples from each tray. We only really needed one of each for the experiment, but it saved them arguing over who got the stickers off the apples, and we get through at least one apple per day each anyway, so the more the merrier!

I set the boys up with a chart each to fill in with the name of the variety, the colour, and a place to rate each out of ten for sweetness, crunchiness and juiciness. The sheets were a chance for the boys to practice their writing without it feeling like a chore, and could be easily used for older kids as a basis for producing some easy graphs, for example a chart of the apple colour frequencies. It was also interesting as it confirmed what I had suspected before, in that Ollie has a different idea to me about what constitutes sweet and sour flavours – he loved the cooking apple and described it as ‘very sweet’ while the ones I regarded as sweet he said didn’t taste so good. The apples all have the same sour components, but the eating apples mask it with a higher dose of fruit sugar, so it’s interesting that Ollie doesn’t pick up on the actual sugar levels as indicative of sweetness. Toby gave lots of varieties ratings of 8 out of 10 because in his words ‘I like writing the squiggly snowman number’.

We used the large Cox apples from the loose apple box in the Supermarket to compare with our usual pre-packed bag

Same variety, different sizes

of ‘lunchbox’ sized small Cox apples to show that there was variation even within a named variety, and to talk about how this came about, such as differences in growing conditions.

We also talked about why the cut surfaces of the apples started turning brown – oxidation – and ways of preventing this happening using things like lemon juice or water. I gave the boys the job of being product developers for a fast food outlet and choosing which variety of apple they would use for a snack pot containing sliced apple, based on their taste testing and their observations about the speed at which the different varieties oxidised. Ollie picked the cooking apple as his favourite, while Toby preferred the Pink Lady. Both agreed though that the Golden Delicious was the best choice for a snack pot though as it didn’t go brown, which led to a discussion about whether the supermarket stocked the tastiest apples or just those that kept well for a long time.

Apples arranged by order of surface oxidation

The kids rave about any activity that involved eating. After this experiment Ollie announced that he wanted to be a food scientist, as well as a professional Lego developer, writer and animator. Toby said he would help Ollie with tasting food science, and as he is going to be a builder he will build Ollie a laboratory, which all sounds pretty good to me.

As an extension to the activity we are planning a trip to the national fruit collection at Brogdale Hall later on in the Spring so we can experience all 1200 of the varieties of apples grown there, which will hopefully be in full blossom when we visit. The boys have also started making notes in the shops of which other types of fruit have a lot of different varieties we can try, strictly for the purposes of science of course!

Note: This post isn’t sponsored or endorsed by Mystery Science, it’s just a resource we use a lot, so I like to give credit where credit is due and say where I have got activity ideas from. If you have kids who don’t like apples, you could substitute for any other type of fruit or vegetable where there are different varieties available to try, for example you could grow different varieties of tomatoes if you have the space, time and patience for a longer running project.

The left-over apples were peeled, cored, chopped and simmered for 15 minutes with a couple of tablespoons of water, a tablespoon of sugar, and a teaspoon of cinnamon to make a delicious stewed fruit pudding.